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John Mulchaey, Director

John Mulchaey is the director and the Crawford H. Greenewalt Chair of the Carnegie Observatories. He investigates groups and clusters of galaxies, elliptical galaxies, dark matter—the invisible material that makes up most of the universe—active galaxies and black holes. He is also a scientific editor for The Astrophysical Journal and is actively involved in public outreach and education.

Most galaxies including our own Milky Way, exist in collections known as groups, which are the most common galaxy systems and are important laboratories for studying galaxy formation and evolution. Mulchaey studies galaxy groups to understand the processes that affect most galaxies during their lifetimes.

As a graduate student, Mulchaey led the team that discovered that some groups are bright X-ray sources. The extent of the emission suggests that the X-rays originated in a very hot, low-density gas called the intragroup medium. X-ray observations of the medium have shown that the temperature is a scorching 10 million degrees. Temperatures this high should quickly disperse; but the intragroup medium does not. Astronomers believe that gravity is binding it. However, the mass required to confine the gas is much higher than the visible group mass. This suggests that galaxy groups are dominated by that elusive material called dark matter, which does not emit light but has a strong gravitational pull.

Although Mulchaey works extensively with space-based, X-ray telescopes, the optical telescopes at Carnegie’s Las Campanas Observatory play a central role in his research. X-ray images alone are not sufficient to uncover the nature of galaxy groups. Follow-up observations with large-aperture optical telescopes, such as Magellan, are necessary to determine galaxy type and distance.

The large Magellan telescopes have allowed Mulchaey to study distant galaxy groups for the first time. He is directly tracing how the group environment affects properties of individual galaxies. These observations suggest that galaxy-galaxy merging is very common in groups. For some groups, the galaxies may continue merging until they form a single massive galaxy. In the last few years, Mulchaey has uncovered several of these “fossil group” systems. Studies of them are proving to have important clues into the likely end state of most groups, including the Local Group, where our Milky Way resides.

Mulchaey received his B.S. in astrophysics from UC-Berkeley and his Ph. D. from the University of Maryland. He was a fellow at the Space Telescope Science Institute and at Carnegie before joining the Carnegie staff. For more information see http://obs.carnegiescience.edu/users/mulchaey

This simple question—asked by the four-year old son of Carnegie’s Juna Kollmeier—started it all. Not long after this initial bedtime query, Kollmeier was coordinating a program at the Kavli Institute for Theoretical Physics (KITP) on the Milky Way while her one-time college classmate Sean Raymond of Université de Bordeaux was attending a parallel KITP program on the dynamics of Earth-like planets. After discussing this very simple question at a seminar, the two joined forces to solve it. Their findings are the basis of a paper published in Monthly Notices

Pasadena, CA— Miguel Roth, director of Carnegie’s Las Campanas Observatory in Chile from 1990 to 2014 and the current representative of the Giant Magellan Telescope Organization (GMTO) in Chile was awarded the Bernardo O’Higgins Order by the Chilean Foreign Affairs Ministry in Santiago today. The honor is in recognition “of his contribution to the development of astronomy in Chile, and for inspiring appreciation and knowledge of astronomy among students and people of all ages.”

The award is the highest civilian honor for non-Chileans. O’Higgins was one of the founders of the Chilean Republic. The award was established in 1965 to recognize

Pasadena, CA—New work from the Carnegie Supernova Project provides the best-yet calibrations for using type Ia supernovae to measure cosmic distances, which has implications for our understanding of how fast the universe is expanding and the role dark energy may play in driving this process. Led by Carnegie astronomer Chris Burns, the team’s findings are published in The Astrophysical Journal.

Type Ia supernovae are fantastically bright stellar phenomena. They are violent explosions of a white dwarf—the crystalline remnant of a star that has exhausted its nuclear fuel—which is part of a binary system with another star.

Pasadena, CA—A supernova discovered by an international group of astronomers including Carnegie’s Tom Holoien and Maria Drout, and led by University of Hawaii’s Ben Shappee, provides an unprecedented look at the first moments of a violent stellar explosion. The light from the explosion's first hours showed an unexpected pattern, which Carnegie's Anthony Piro analyzed to reveal that the genesis of these phenomena is even more mysterious than previously thought.

Their findings are published in a trio of papers in The Astrophysical Journal and The Astrophysical Journal Letters. (You can read them here, here, and here.)

The fund supports a postdoctoral fellowship in astronomy that rotates between the Carnegie Science departments of Terrestrial Magnetism in Washington, D.C., and the Observatories in Pasadena California.

The Earthbound Planet Search Program has discovered hundreds of planets orbiting nearby stars using telescopes at Lick Observatory, Keck Observatory, the Anglo-Australian Observatory, Carnegie's Las Campanas Observatory, and the ESO Paranal Observatory. Our multi-national team has been collecting data for 30 years, using the Precision Doppler technique. Highlights of this program include the detection of five of the first six exoplanets, the first eccentric planet, the first multiple planet system, the first sub-Saturn mass planet, the first sub-Neptune mass planet, the first terrestrial mass planet, and the first transit planet.Over the course of 30 years we have

The Giant Magellan Telescope will be one member of the next class of super giant earth-based telescopes that promises to revolutionize our view and understanding of the universe. It will be constructed in the Las Campanas Observatory in Chile. Commissioning of the telescope is scheduled to begin in 2021.

The GMT has a unique design that offers several advantages. It is a segmented mirror telescope that employs seven of today’s largest stiff monolith mirrors as segments. Six off-axis 8.4 meter or 27-foot segments surround a central on-axis segment, forming a single optical surface 24.5 meters, or 80 feet, in diameter with a total collecting area of 368 square meters. The GMT

Along with Alycia Weinberger and Ian Thompson, Alan Boss has been running the Carnegie Astrometric Planet Search (CAPS) program, which searches for extrasolar planets by the astrometric method, where the planet's presence is detected indirectly through the wobble of the host star around the center of mass of the system. With over eight years of CAPSCam data, they are beginning to see likely true astrometric wobbles beginning to appear. The CAPSCam planet search effort is on the verge of yielding a harvest of astrometrically discovered planets, as well as accurate parallactic distances to many young stars and M dwarfs. For more see http://instrumentation.obs.carnegiescience.edu/

Staff Associate Kamena Kostova joined the Department of Embryology in November 2018. She studies ribosomes, the factory-like structures inside cells that produce proteins. Scientists have known about ribosome structure, function, and biogenesis for some time. But, a major unanswered question is how cells monitor the integrity of the ribosome itself. Problems with ribosomes have been associated with diseases including neurodegeneration and cancer. The Kostova lab investigates the fundamental question of how cells respond when their ribosomes break down using mass spectrometry, functional genomics methods, and CRISPR genome editing.

Sally June Tracy applies cutting-edge experimental and analytical techniques to understand the fundamental physical behavior of materials at extreme conditions. She uses dynamic compression techniques with high-flux X-ray sources to probe the structural changes and phase transitions in materials at conditions that mimic impacts and the interiors of terrestrial and exoplanets. She is also an expert in nuclear resonant scattering and synchrotron X-ray diffraction. She uses these techniques to understand novel behavior at the electronic level. Tracy received her Ph.D. from the California Institute of

The Ludington lab investigates complex ecological dynamics from microbial community interactions using the fruit fly Drosophila melanogaster. The fruit fly gut carries numerous microbial species, which can be cultured in the lab. The goal is to understand the gut ecology and how it relates to host health, among other questions, by taking advantage of the fast time-scale and ease of studying the fruit fly in controlled experiments.

Nick Konidaris is a staff scientist at the Carnegie Observatories and Instrument Lead for the SDSS-V Local Volume Mapper (LVM). He works on a broad range of new optical instrumentation projects in astronomy and remote sensing. Nick's projects range from experimental to large workhorse facilities. On the experimental side, he recently began working on a new development platform for the 40-inch Swope telescope at Carnegie's Las Campanas Observatory that will be used to explore and understand the explosive universe.

Nick and his colleagues at the Department of Global Ecology are leveraging the work on Swope to develop a new airborne spectrograph that will be